ADS-B is a surveillance technology for tracking aircraft as part of the Next Generation Air Transportation System and will be replacing some ground-based radar systems as the primary surveillance method for controlling aircraft. ADS-B enhances safety by making an aircraft visible, real-time, to Air Traffic Control (ATC) and to other appropriately equipped ADS-B aircraft with position and velocity data transmitted every second. ADS-B also provides the data infrastructure for inexpensive flight tracking, planning, and dispatch.
ADS-B uses conventional Global Navigation Satellite System (GNSS) technology and a relatively simple broadcast communications data-link (ADS-B unit) as its fundamental components. ADS-B consists of two different services, a transmitted “ADS-B Out” signal and a received “ADS-B In” signal. There are two types of certified ADS-B data links, but the one most commonly used by commercial air transport airplanes operates at 1090 MHz, essentially a modified Mode S transponder. The other ADS-B standard currently in use is known as Universal Access Transceiver (UAT) and operates at 978 MHz. The International Civil Aviation Organization (ICAO) has promulgated standards for both these systems and a third system (so called VHF data link Mode 4) that operates in the VHF frequency band (118-136). The description of the invention herein considers only the ADS-B systems operating in the USA (i.e. Mode-S extended squitter at 1090 MHz and UAT at 978 MHz). However, the general principles can be applied at any frequency band and could be applied to other ADS-B systems such as VDL Mode-4.
An ADS-B capable aircraft uses an ordinary GNSS (GPS, GLONASS, Galileo, etc.) receiver to derive its precise position from the GNSS constellation and then combines that position with aircraft state information, such as speed, heading, altitude and flight number. This information is then simultaneously broadcast via the “ADS-B Out” signal to other ADS-B capable aircraft and to ADS-B ground, or satellite communications transceivers which then relay the aircraft's position and additional information to ATC centers in real time.
However, ADS-B includes no provisions for authenticating ADS-B signals received from transmitting sources. Spoofing ADS-B signals is relatively simple and may limit the ultimate usefulness of ADS-B. GNSS jamming devices are widely available and ADS-B spoofing may be done with off-the-shelf equipment. Ground systems can use multi-lateration or cross check with radar systems to detect bogus ADS-B reports. However, both of these options have significant costs. It is with respect to these and other considerations that the disclosure herein is presented.